Dry kiln



Feb. 5, 1935. M 1.. MUELLER DRY KILN Filed Feb. 9, 1951 2 Sheets-Sheet 1 INVENTOR Mom TZ L. P705457 ATTORNEY Feb. 5, 1935. M. NIIIUVEILFER I DRY KILN Filed Feb. 9, 1931 Patented Feb. 5, 1935 PATENTS-OFFICE f DRY KILN" Moritz L. Mueller, :Seattle, Wash.

Application February 9,

1931, semi No. 514,436 1 1-Glaim. (Cl.

This invention relates to-improvements in dry kilns and particularly to kilns for th'e drying of lumberwherein a forced circulation of the drying medium'is employed to expedite the .drying ,op--

5. eration.

Explanatory to the present; invention it will herebe stated that in those types'of kilns now generallyused iorthe drying of lumbenfthe. air or gaseous-content of the 'kiln-isforcibly c'ir;- culate'd through the stock to be dried by .the action of. rotating fans, .a nd during-:thec'ourse of circulation, it is deliver'ed through grids, or banks of heated pipes to maintain itat the proper temperaturea'and relative humidity for proper drying.

It isthei-usua'l practice to so locatetth'e stock to be dried with-inithe-kiln that it serves 'in-con-ibina tion with the fan duct to divide the kiln, thus forming a pressure chamber at oneside orthe stock, anda suction chamber. at the other side. With this arrangement the action of the -fans isto draw ainrrcm tnesuctien chamber andto deliver-it' 'in to the pressure chamber-, imm which latter chamber it is drawn or forced thrQug h -inE t'e'rs'tics 'pivided in the stock backto' the suction chamber. It i has been the practiceheretofore in'such arrangements to locate the heating pipes in the passages from the fan duct leading to and from the pressure and suction chambers, and

iii-such arrangementsfit is-requ'fi'ed easementc'ul'ated' drying medium be twice forced' thro ugh the pipe grids in each cycle 'through tlie stock.-

-Itwill readily'be obvious to those familiar, with the drying of lumber, or the like, that when steam heating pipes are used' inl a 'desiredor heating of the. air; andthe air is forced between the .closely placed. pipes, they will materially-free. tard circulation, and this will result in the 'consumption ofrmore power to propel the fans to maintain the rate of circulation or volume of air necessary for successful commercial operations. Furthermore, fans of the characteremployed for air circulation inkilns ofthis typeare very sensitive to back pressure, thus any retarding in flue-nee in the path of circulation very materially increases the power required to propel the. fans. f In view of the above explanation'it has been the principal object of the present invention to provide a dry kiln construction employing fans of the usual'chara'cter for creating a'fo'rcedcircula tion of'the drying mediumyand to employ means for heating the circulated medium, but to so locate'the' said means that they will not retard, or'otherw ise interfere- With'flo'w'or circulation.

" Mere specifically statd; the sweeter metres required number to insure eifec tive and: proper ent invention is to construct a dry kiln employing .forced circulation'of air and in which the air passages to; and from the pressure and suction sides of the kiln'are unobstructed'by any interposition ofste'am'pipes, or other heating elements, '5:

through which the air is circulation; 1 Itis also anjobjectof the present invention to provide .baifies, or deflectors, against which theair is directed, during its flow or travel to and from the fans, and to heat these, baflies and to so locate them in the kiln that they will facilitate the proper directional flow or circulation of the drying medium rather than to retard it, and. will heat the medium byreasonof its impingement 1 with their heated surfaces. I

.It is 'also'an object of the invention to provide for the use-of electric motors for operation of the air circulating fans which are insulated in novel manner to successively resist the excessive heat within *the kilng'which heretofore has rendered use of electric."motorspimpractical without provision of special cooling equipment.

Other objects of the inventiOrireside in the various details of construction, in the combination of parts and in their mode of operation and relationship to each other, as will hereinafter beiiully described.

in accomplishing theseand other objects of the invention, I have provided the improved details ofuconstruction, the preferred forms of which are illustrated in the accompanying drawings where- Fig; 1 is a cross sectional view of a dry kiln embodying the present invention.

, Fig.-=2Yis a horizontal sectional View of a portion of; theK-diy kilntaken substantially on the line 2 -2 in Fig. 1.

Fig. 3 is a transverse sectional view illustrating an alternative form of construction. 40 Fig.4 is an enlarged sectional view'of a coristruction detail.

Fig.-i5tis a sectional detail of a kiln embodying the: present invention, designed for drying edge stacked lumber.

Referring more in detail to the drawingsin Figsfland 2, '1' designates,;in its entirety, adry kiln embodying the present invention. Thiskiln comprises opposite side walls 2 and 3, a top wall 4, and "a bottom wall orv floor designated at 5. Transversely of the kiln arerhorizontal beams 6 which support thereon parallel, track-forming rails 7- 7 along which" wheel-supported lumber trucksgasdesignated at 8, are movable. I it "Oh the truck 8; asillustratedin Fig. 1, is apile 0 required, to pass during 9 of lumber or other material to be dried, this pile being arranged to provide interstices 10 horizontally therethrough from the chamber or passage 11, formed between the pile and side wall 2, into the chamber or passage 12, formed between the pile and the opposite side wall 3 of the kiln. Extended lengthwise of the kiln, centrally below the cross beams 6, is a partition wall 13 provided at regularly spaced intervals with openings 14 within which fans 15 are disposed.

In Fig. 2 I have illustrated the fans as each having a direct mounting on an electric motor 18 supported by a frame structure 19, however it is to be understood that any desirable driving means may be provided. In some instances, a line shaft may be used to better advantage. When electric motors are employed it is quite essential, because of the excessive heat within the kiln, that the windings thereof be properly and eifectively insulated with a substance which will not be destroyed or rendered ineffective by reason of the heat within the kiln. It is to be understood that temperatures up to 240 F. are used in lumber drying, and this is above the melting point of the rubber composition usually used for insulating the motor coils. The melting of this insulation is destructive to motors, but I have overcome this difliculty by using motors in which the copper windings are insulated by asbestos coatings which will effectively resist heat up to 400 F. It is also desirable to seal the motor construction in a manner suitable for keeping all windings protected from acids, vapors, etc., which are given off in the drying of lumber. The motor should also be provided with a drain hole for draining out condensation. Motors may have reduction gearing incorporated therewith when it is desired to operate the fan at a low speed, or the fans may be driven direct from the motor shaft.

In the arrangement of Figs. 1 and 2, the passage of air across the top of the lumber pile from one side of the kiln to the other is prevented by plates 20 extending downwardly from the roof 4 closely adjacent the top and sides of the lumber pile.

In the course of operation, the fans 15, are revolubly driven by the motors to create a forced circulation of air, drawing it downwardly from the chamber at one side of the lumber pile and delivering it forcibly into the chamber at the other side, from which it flows through the horizontal interstices in the pile back to the starting point. Reversal of direction of rotation of the fans effects a reversal in the direction of flow of the drying air.

As was previously stated, the circulated drying medium is ordinarily heated by the placing of steam pipes, or coils of heated pipes, within the passages leading from the suction and pressure chambers to and from the fan duct. These steam pipes are ordinarily used in large numbers in order that proper heating may be maintained, especially at the start of a drying operation, and their use materially interferes with the flow of air and consequently materially increases the power that is required to operate the fans. The present invention has overcome this undesirable result by elimination of pipes and coils through which the air must flow and by the substitution therefor of heated deflectors, located at points in the kiln where deflectors are ordinarily used to obtain proper directional flow of the medium. Fig. 1 illustrates a preferred deflector arrangement for kilns where the fan system is located beneath the stock. Each of these deflectors comprises a bank of steam pipes 24 supported by brackets or bars 25. The pipes extend lengthwise of the kiln in close relation to each other and may be placed in contact with each other if this is desired, but it is preferred that they be slightly spaced apart so that air may pass entirely around them. The deflectors thus formed by the banks of steam pipes are located in the opposite lower corners of the kiln in an inclined position so that air forcibly delivered from the fanswill strike'the deflector at one side of the kiln andwill be deflected upwardly thereby and air flowing downwardly from the chamber at the other side of the lumber pile will impinge with the other deflector and be deflected laterally toward the fans. It will be observed that the air thus twice engages with heated surfaces during each cycle. While I have illustrated the deflectors in Fig. 1 as being perfectly straight, it is to be understood that they may be straight, or curved radially, or shaped to give a stream-line effect if this is desired.

In Fig. 3 I have illustrated an arrangement embodied by this invention, adapted to kilns in which the fan system is located above the lumber pile. In this latter arrangement the lumber truck travels on rails 26 mounted on the floor of the kiln and the kiln is divided centrally above the stock or lumber pile by a longitudinal partition 27 with openings 28 in which fans 29 are mounted. The deflectors 30 and 31 are made up of closely placed steam pipes 32 supported by brackets 33. In this construction air delivered by the fans impinges against the deflector at one side in the same manner as in the construction of Fig. 1, and is deflected downwardly. It flows through the stock, thence upwardly to impinge the bafile at the other side, and then flows to the fans.

In either constructon illustrated, the usual ventilators for admittance of cold air and outlet of heated airmay be employed and these would be located at places found to be most practical or in the places where such ventilators are ordinarily placed. g

In Fig. 4 I have illustrated an arrangement of pipes whereby the delivery of air from the fans into the pressure chamber may be directed or controlled.

In this arrangement the deflector is formed by two sections orbanks of pipe, 38 and 39, in planes forming an obtuse angle with each other. A space as at 40 is provided between the two deflector sections and also a space 41 is provided between the side-wall and lower edge of deflector section 39. This construction permits air to be delivered through the space 40 into the corner back of the deflector and it is discharged directly downward through space 41 along the side'of the kiln. The

air delivered by the fan is deflected downwardly by the deflector 39 and the resultant angle after it meets the air from opening 41, is dependent on the angular relationship of the two streams. Thus by proper angular placement of deflector 39, the air may be delivered or directed downwardly as desired into the pressure chamber.

In Fig. is an arrangement for edge stacked lumber. In this arrangement an air duct 50 is formed longitudinally of the kiln below the track by two longitudinally extending plates 51 and 52 which terminate at their upper edges closely adjacent opposite sides of the lumber truck on which the stock is piled, and converge downwardly toward each other and are joined by a horizontal wall 53, in which openings 54 are provided for horizontal fans 55. Each fan is connected with a driving motor 56 or other suitable propelling means.

The passages at opposite sides of the lumber pile communicate with the chamber formed within the base of the kiln, and in operation the fans deliver air drawn from this chamber, upwardly through the vertical interstices in the stock, from whence it flows in opposite lateral directions, passing downwardly along opposite sides of the stock to the bottom chamber.

In this latter instance the downflowing air engages inclined deflectors 58-58 along the outer walls and is directed inwardly. Then it engages a second set of deflectors 60 and is directed upwardly to the fans. The deflectors 58--58 face inwardly and upwardly, thus the air streams twice engage heated surfaces in pasing to or from the fans. These deflectors are formed of steam pipes or heated elements of any other suitable character, arranged as are the pipes of the deflectors previously described.

It is to be understood that in any of the constructions illustrated steam or other heated, fluid medium is delivered to the pipes and is circulated therethrough in the usual well-known manner. For example, as shown in Fig. 2, the pipes are all connected at one end of the kiln to a header '70 to which a steam supply pipe 71 is attached. A leader '72 connects the pipes at their other ends and an outlet pipe 73 leads from this leader.

It is not intended that the present invention be confined in use to any particular type of kiln or fan system, but that it cover the use of heated deflectors or baflles for heating the circulated drying medium by reason of contact therewith, and that these deflectors or bafiles be so located as to least retard the air flow, and to avoid the necessity of air flowing through the heating coils or elements, as is ordinarily done.

Having thus described my invention, what I claim as new therein, and desire to secure by Letters-Patent, is:

- In a drying kiln including means therein for supporting stock to be dried in a manner to provide air passages at opposite sides of the stock, a partition wall dividing the kiln above the stock and having openings therein, fans in the said openings for creating forced circulation of air transversely of the kiln and deflectors located in the kiln at opposite sides of the fans and against which the air in circulation will contact and will be directed in the passages to and from the fans, said deflectors comprising heated surfaces providing intermediate spaces for the passage of part of the air from the fans through the deflectors and said deflectors being spaced from the walls of the kiln whereby a passage is provided for the outflow of that air which passes through the deflectors for delivery in a stream which meets the deflected stream of air from the deflectors to affect its directional course.

MORITZ L. MUELLER. 

